The present invention relates to a method and apparatus for driving and controlling an improved solenoid impact imprinter commonly used to emboss information onto a common credit card.
Automated embossing systems have found wide acceptance in the field. Two such systems are disclosed in (1) U.S. Pat. Nos. Re 27,809 to Drillick and 3,820,454 to Hencley et al. and (2) U.S. Pat. No. 3,820,455.
The present method, apparatus and improved solenoid structure builds on the invention disclosed in the application of Warwick et al., Ser. No. 204,499, hereby incorporated by reference. The Warwick application discloses a solenoid system in which the solenoid coil is energized in two stages, i.e., by a first and second current pulse. In the Warwick disclosure, as in the present invention, the first pulse is intended to bring the print elements into contact or close proximity with the material to be imprinted; the second pulse is intended to imprint the chosen material. Because the print elements are already in contact or in close proximity with the material to be imprinted when the embossing current pulse is applied, the loud impact noise of the printing elements striking the material is eliminated, thus providing an embossing operation with little noise. Using the two pulse method further reduces the velocity of the moving parts which also helps to reduce noise.
In addition to the noise problem, solenoid driven embossing systems generally encounter the problem of providing a solenoid body assembly (1) that limits heating of the solenoid structure due to eddy-current losses in the material used to construct the solenoid body assembly and (2) that enhances the durability and precision of the solenoid embossing structure. The prior art shows the use of magnetic materials such as steel for the solenoid body assembly.
In addition to other novel and patentable features, the present method, apparatus and improved solenoid structure improves on the two pulse method for energizing the solenoid coils. The present invention also provides an improved solenoid system to further enhance the durability and precision of the solenoid embossing system and to reduce eddy-current losses.